This article elucidates the impacts of the COVID-19 pandemic on public mental health and mental health needs, in addition to providing evidence from multiple current online psychological interventions. Moreover, Psychological First Aid (PFA), developed by the World Health Organization, is introduced as an evidence-based, brief psychological intervention that is used to immediately assist patients of diverse age groups and their families to work through their psychological crises in the aftermath of a disaster, such as COVID-19. This article can provide useful information to governments and health care professionals regarding public mental health during the pandemic, thus enabling them to provide adequate psychological interventions. Such appropriate support can help to reduce the short-term physical and psychological distress caused by traumatic events resulting from the pandemic, to foster the long-term adaptive functioning and overall mental health of patients and the public, and to improve societal security.